Wednesday, July 13, 2016

Mechanics of DRS grist control

Let's say I want to spin  5,600 ypp worsted singles.  Such singles are competent with twist between ~5.3 tpi and 13.34 tpi, and I want to average ~9 tpi.

I put on my "10s" flyer whorl, and start spinning.  The first 1/8 of an inch of yarn on the bobbin will have a twist of  ~ 10 tpi.  The next quarter inch of yarn on the bobbin will have twist of ~ 9 tpi, and then the next 1/8 inch of single on the bobbin will have twist of ~ 8 tpi.  Now there is half an inch (300 yards) of single on the bobbin with a average twist of ~ 9 tpi. At that point, I flip the drive band over to the "20s" grove on the flyer whorl, and with the larger effective bobbin diameter, I am back to spinning at about, 11 tpi which tapers down to ~ 9 tpi as the bobbin fills.

Some drafting skill is required. If  I want consistent grist, then twist per inch (and firmness of the single) varies.  If I want consistent texture, then the grist varies a bit.  In either case  control is better than can be achieved with Scotch Tension or most modern DD  flyer/ bobbin assemblies. And, in either case the process can be ridiculously fast, so the fingers can stay busy.

If I want 20,000 ypp or thinner singles, I put the appropriate flyer whorl on, and start spinning.  In this case, I can spin a whole 560 yd/ 10 gram  hank, before the twist changes significantly.   Such hanks wound off on to 10-gram capacity,  plying bobbins will yield a 500 yard hank of  6-ply hoisery yarn with a grist of just over 3,000 ypp (7 m/g).   At 3,000 rpm one can spin such singles at 200 yards per hour, so a hank of such hoisery yarn is a couple days work, with bright eyed, nimble fingered younglings going much faster.  The Competitor is on the wheel right now, and with a fresh drive band is perfectly happy running at 400 yards per hour, so a hank of

Even 1,200 yards of  fine singles is only ~12 grams and does not change the effective bobbin diameter enough to significantly change the twist.  Thus, if one is spinning "fines"  (Merino or Rambouillet spun at its spin count, e.g., 40,000 ypp/ 30 tpi) , one can spin fast all morning without winding off.

Remember, With DRS, If you stop single from entering the orifice as is done with ST or modern DD wheels to accumulate twist, break off will be instantaneous.  You can draft faster than take-up, so that there is slack between the drafting triangle and the orifice, without a problem.  For example, this occurs when a thick region occurs in the proto-single and it has to be thinned out.  In this case the single MUST continue to feed into the orifice, or  it will break off.

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